MICROSTRUCTURE MODIFICATION OF Cu0.2Ag2.8SbSeTe2 THROUGH

Cu0.2Ag2.8SbSeTe2 is new potential thermoelectric compound that exhibits very low thermal conductivity and a region of glass-like thermal conductivity. The compound phase segregates into AgSbTe2 and Ag2Te phases with Se and Cu acting as isoelectronic dopants. Backscatter SEM imaging is used to study the resulting microstructure. Normally cast samples exhibit cracks forming near the interfaces of the two phases. In this work we show that the cracks are caused by a low temperature monoclinic to cubic phase transition that occurs in the Ag2Te phase. We demonstrate that through rapid quenching we can control the size and shape of the phase domains eliminating the interfacial cracks. TEM data showing nanocrystaline domains suggest a possible explanation for the amorphous thermal conductivity